Step 1. Emulator

Step 2. BIOS

Download GBA Bios, you can find it on [here]. Place it in the folder folder the roms are in.

Step 3. Download

Download any ROM from this or any file-safe website onto your computer.

Step 4. Connect

Connect the USB cord to your Android mobile device then to your Computer. On your Android device, you will get a notice such as "Turn ON USB Storage" (this differs on phones). Just make sure your phone is connected to your computer.

Step 5. Create

Create a folder called ROMS within your Android mobile device (organization). You can do this by accessing your Android device through My Computer, it will show a new device there. Open it then create the folder.

Step 6. Transfer

Transfer all games you've downloaded into the ROMS folder on your Android mobile device. Don't forget to transfer the BIOS File as well. Remember to click "Turn OFF USB Storage" when you are done! This safely un-mounts your SD Card.

Step 7. Play

Open up your emulator, if you needed a BIOS, be sure to load it first. You can do this by going to MENU -> SETTINGS -> BIOS FILE (varies per emulator).

Afterwards, hit the back button on your phone till you reach the black screen with files, then navigate go to your ROMs folder (/sdcard/download/roms/ or /mnt/sdcard/download/roms). Just double tap the game of your choice to start playing.

If the game does not play correctly, you may need to modify settings such as frame rate or enabling special features. OH yeah....most importantly, make sure to have fun.